The present invention relates to rotary mechanical seals and more particularly to gas face seals.
Rotary mechanical seals are used in a wide variety of rotary shaft devices including blowers, compressors, vacuum pumps and expanders. The seals provide a barrier between the gas working chamber and the external environment. The seals minimize loss of working fluid to the environment. These seals are positioned at the interface or penetration of the rotating shaft with the stationary working chamber or housing. Mechanical seals may be of the circumferential type or of the face type or controlled gap type.
A wide variety of face seals have heretofor been proposed. These seals generally include a shoulder or sealing element fixed to the rotating shaft so as to rotate therewith. A nonrotating seal element or face seal ring is supported on the housing and restrained so as to be nonrotatable. The shoulder and face seal ring define opposed sealing faces or surfaces. Provision is made for urging the surfaces towards one another.
Operation of such seals requires that a small but finite gap or separation be maintained between the opposed sealing surfaces. The finite gap is achieved by a combination of hydrostatic and hydrodynamic gas forces. An example of a gas seal may be found in U.S. Pat. No. 3,499,653 entitled ROTARY MECHANICAL SEAL OF THE GAP TYPE and which issued on Mar. 10, 1970 to Gardner. The seal disclosed therein includes a rotor or shoulder mounted on a shaft and defining a radially disposed sealing surface. A seal ring is urged towards the rotor by a plurality of springs. The seal face of the seal ring defines a plurality of spiral grooves. The grooves create a hydrodynamic lift to create the gap or separation between the opposed sealing elements. Examples of other gas seals may be found in U.S. Pat. No. 3,640,541 entitled HYDRODYNAMIC LIFT-TYPE FACE SEAL and which issued on Feb. 8, 1972 to Taschenberg and U.S. Pat. No. 4,212,475 entitled SELF ALIGNING SPIRAL GROOVE FACE SEAL and which issued on Jul. 15, 1980 to Sedy.